The present invention relates to air circulation devices and, more particularly, air circulation devices of the squirrel cage type.
Centrifugal fans or blowers, also commonly referred to as squirrel cage blowers, are ubiquitous. They are used in such things as home appliances, office equipment, and automobile heater/AC units. The operating principal is the same for all centrifugal blowers. The air is drawn in at the inlet by a rotating impeller which is driven by a motor and contains a number of passages arranged in a spiral pattern. On flowing through these passages the air is given an acceleration and emerges at the outlet under pressure from the blower housing.
Such blowers are also characterized by a cut-off area formed at the intersection of the outlet housing and the radial housing which encases the impeller (see FIG. 3). One problem with these blowers is that the cut-off area causes an abrupt change in the tangential and radial air flow area that is available. That is, the air flow through the impeller is restricted abruptly as it passes the cut-off area. This sudden change the in the air flow area disrupts the flow pattern and causes a large pressure pulse to occur at regular timed intervals, which in turn causes a near monotone sound. Thus, there is a need in the art for an improved centrifugal blower or squirrel cage type blower that causes a much smaller pressure pulse to occur at the cut-off and thus reduces noise and vibration and improves efficiency.
It can therefore be seen that there is a real and continuing need for the development of an improved squirrel cage type blower that reduces noise and vibration and improves efficiency.
The primary objective of the present invention is the provision of an improved squirrel cage type blower that reduces or eliminates the abrupt change in air flow area at the cut-off area.
Another objective of the present invention is the provision of an improved squirrel cage type blower that effects a gradual change in the air flow area to cause a much smaller pressure pulse to occur, and hence, reduces noise and vibration.
Another objective of the present invention is the provision of a method of reducing the noise and vibration and improving the efficiency of a squirrel cage type blower.
Still another objective of the present invention is the provision of an improved squirrel cage type blower that is efficient in operation, economical to manufacture, and durable in use.
These and other features, objectives, and advantages will become apparent to those skilled in the art with reference to the accompanying specification.